August 2017

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August 2017

Sea-ice cover for August 2017

Sea-ice cover for August 2017. The pink line denotes the climatological ice edge for August for the period 1981-2010. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service) Download the original image

Sea-ice was much less widespread in August 2017 than in the average for August from 1981 to 2010.

Arctic sea-ice was either absent or at a lower concentration than normal almost everywhere. Ice cover was especially below average in a region extending outwards into the Arctic Ocean from the Beaufort Sea and the East Siberian Sea.

Antarctic sea-ice cover was also lower than average overall. It extended less to the north than is normal for August in all but one sector, although concentrations close to the northern limit of sea-ice were also higher than average in two other sectors.

Sea-ice cover anomaly for August 2017 relative to the August average for the period 1981-2010. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service) Download the original image

Surface air temperature anomaly for August 2017 relative to the August average for the period 1981-2010. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service) Download the original image

Corresponding maps of surface air temperature anomalies tend to show relatively warm conditions over the regions of below-average sea-ice cover, and relatively cool conditions where there was above-average sea-ice cover. This can occur as a response of surface air to having relatively warm ice-free sea rather than sea-ice beneath it, or as a common response of ice cover and air temperature to anomalies in atmospheric circulation. The relationship weakens when temperatures rise to reach values that then persist at close to 0°C, as melting takes place. This happens over the Arctic Ocean in summer. The August 2017 temperature anomalies are accordingly small over this region.

Bands of relative warm temperatures occur over the regions of below-average sea-ice cover around Antarctica in August 2017, in contrast to the colder than average winter conditions found for the month over much of the continent and surrounding sea ice.

Area of the Arctic (upper) and Antarctic (lower) covered by sea-ice, shown as monthly anomalies relative to 1981-2010. The darker coloured bars denote the August values. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service)Access to data Download the original image

Variability and trends in the areas of Arctic and Antarctic sea-ice are evident in graphs of time series of monthly anomalies relative to average 1981-2010 values. The principal feature for the Arctic is a downward trend that is prominent after the year 2000. Summer and autumn have been the seasons that have mainly seen uncharacteristically low sea-ice cover in recent years, but recent years have also seen relatively low cover late in the winter, when sea-ice reaches its annual maximum. Arctic sea-ice area for the month of August was not as low in 2017 as in some recent years, but the August 2017 value was nevertheless lower than any August value prior to 2011. It should, however, be noted that the dataset used here overestimates cover in August 2007, for which there is evidence of similar or slightly lower cover than in 2017.

Variability rather than trend predominates for the Antarctic. Spells of markedly above-average sea-ice cover occurred in 2007-2009 and 2013-2015. Conversely, Antarctic sea-ice cover has been substantially below average over the past year or so. Anomalies in November and December 2016 were more negative than for any month in the period from 1979. Antarctic sea-ice cover was lower in August 2017 than in any August other than August 2002.

Annual range of sea-ice area from summer minimum to winter maximum for the Arctic (upper) and Antarctic (lower) based on monthly average values from 1979 to 2016. Maxima and minima for 2017 are based on all months of the year to date. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service)Access to data Download the original image

An alternative view is provided by graphs of minimum and maximum monthly average sea-ice area for each year. Declining sea-ice cover is evident for the Arctic in both minimum and maximum annual values. Variability is again seen to predominate for the Antarctic, where record or near-record low and high annual minima and maxima occur within a few years of each other.

March is usually the month for which the average Arctic sea-ice area is a maximum, although in some years February is the month with most cover. September is usually the month with the lowest average Arctic cover, but cover is sometimes lower for August. February was the month with the highest average Arctic sea-ice area in 2017, and September was the month with minimum cover in 2016.

February is invariably the month with the lowest average Antarctic sea-ice area in this data record. February 2017 is no exception. September is usually the month with the largest average Antarctic cover. October has the largest cover in one year of the data record and August has the largest cover in two years, one of which is 2016.

The sea-ice analysis page explains more about the nature, production and reliability of the data and information presented here.